Phosphorus-containing lubricating compositions

ABSTRACT

Lubricating compositions comprising a major proportion of lubricating oil and a minor proportion of at least one additive of the formula: 
     
         Y.sup.a --S--Y.sup.b 
    
     wherein Y a  corresponds to ##STR1## and Z is ##STR2## and each R 1  and R 2  is independently hydrocarbyl, hydrocarbyloxy and hydrocarbylmercapto of one to about 30 carbon atoms; R 3  is hydrogen or hydrocarbyl of up to about 10 carbon atoms; R 4  is hydrogen or lower alkyl; R 5  and R 6  are each independently hydrogen, hydrocarbyl, hydrocarbyloxy and hydrocarbylmercapto of one to about 10 carbon atoms; R 7  is hydrogen or hydrocarbyl of one to about 30 carbon atoms; each X is independently oxygen or divalent sulfur; n is zero or an integer of one to about 10; n&#39; is zero or an integer of one to about 9; Y b  is 
     
         --R.sup.8 --H or --R.sup.8 --S--R.sup.9 
    
     wherein R 8  is a divalent hydrocarbyl group of one to about 30 carbon atoms and R 9  is hydrogen or Y a  have increased resistance to oxidative degradation and anti-wear properties.

It is known in the prior art that certain phosphorus acid compounds canbe reacted with certain unsaturated aldehydes or ketones to formadducts. These adducts can be used in lubricant compositions asantioxidants and corrosion inhibitors and for imparting antiwear andload-carrying characteristics to lubricating oils. (See, for example,U.S. Pat. Nos. 2,632,020; 2,794,041; 2,876,245; 2,948,682 and3,644,206.)

It has not been previously known or suggested, however, that theseadducts be further reacted with certain thiols or dithiols to form theadditives of this invention or to incorporate these additives inlubricant and functional fluid compositions such as those of the presentinvention.

This invention relates to new compositions of matter and to lubricatingand functional fluids containing them. More particularly, thecompositions of this invention are additives made by the reaction ofcertain phosphorus acid compounds with certain aldehydes or ketones andcertain thiols or dithiols. This invention also relates to lubricant andhydraulic fluid compositions comprising these additives as well asprocesses for preparing these additives.

More specifically the compounds of the present invention correspond tothe formula:

    Y.sup.a --S--Y.sup.b

wherein Y^(a) corresponds to ##STR3## and Z is ##STR4## wherein each R¹and R² is independently a member selected from the group consisting ofhydrocarbyl, hydrocarbyloxy and hydrocarbyl mercapto of one to about 30carbon atoms; R³ is hydrogen or hydrocarbyl of up to about 10 carbonatoms; R⁴ is hydrogen or lower alkyl; R⁵ and R⁶ are each independentlyselected from hydrogen, hydrocarbyl, hydrocarbyloxy andhydrocarbylmercapto of one to about 10 carbon atoms; R⁷ is hydrogen orhydrocarbyl of one to about 30 carbon atoms; each X is independentlyoxygen or divalent sulfur; n is zero or an integer of one to about 10;n' is zero or an integer of one to about 9; Y^(b) is

    --R.sup.8 --H

or

    --R.sup.8 --S--R.sup.9

wherein R⁸ is a divalent hydrocarbyl group of one to about 30 carbonatoms and R⁹ is hydrogen or Y^(a).

The phosphorus acid compounds used in the preparation of the additivecompositions of the present invention are of the formula: ##STR5##wherein each X is independently oxygen or divalent sulfur and R¹ and R²are each independently a member selected from the group consisting ofhydrocarbyl, hydrocarbyloxy and hydrocarbylmercapto of one to about 30carbon atoms. Preferably, X is oxygen and each R¹ and R² containsbetween one to about 18 carbon atoms; more preferably both R¹ and R² areindependently alkoxy or alkylphenoxy groups containing one to about 18carbon atoms and each X is a divalent sulfur atom.

When reference is made in this specification and in the appended claimsto the term "lower" in conjunction with another group such as loweralkyl, lower alkoxy, lower alkylmercapto, and the like, it is intendedto include all such groups having a total carbon content of up to seven.For example, "lower alkyl" includes all straight and branched chainalkyl groups of up to seven carbon atoms such as methyl, ethyl, propyl,isopropyl, tert-butyl, n-heptyl, etc.

When reference is made in this specification and the appended claims tohydrocarbyl, hydrocarbyloxy, hydrocarbylmercapto, aliphatic or alkylgroups, it is to be understood, unless expressly stated to the contrary,that analogous substituted groups referred to as substantiallyhydrocarbyl, substantially hydrocarbyloxy, substantiallyhydrocarbylmercapto, substantially aliphatic, and substantially alkylgroups are also contemplated. The description of these groups as beingsubstantially hydrocarbyl means that they do not contain anynon-hydrocarbyl substituents which would significantly alter the generalhydrocarbyl characteristics or properties of the group relevant to theiruses as described herein. Thus, it is obvious in the context of thisinvention, for example, that a purely hydrocarbyl C₂₀ alkyl group and aC₂₀ alkyl group substituted with a methyl mercapto or methoxylsubstituent at a point in the chain remote from other polar (i.e.,non-hydrocarbyl) groups, would be substantially equivalent in itsproperties with regard to its use in this invention and would, in fact,be recognized as substantially equivalent by those of ordinary skill inthe art. That is, one of ordinary skill in the art would recognize bothsuch groups to be substantially hydrocarbyl, etc.

Non-limiting examples of substituents which do not significantly alterthe hydrocarbyl, etc., properties or nature of hydrocarbyl, etc., groupsof this invention are the following:

Ether groups (especially hydrocarbyloxy and particularly alkoxy groupsof up to ten carbon atoms)

Amino groups (including mono- and disubstituted amino groups such asmono- and dialkyl amino or mono- and diaryl amino and the like, e.g.,ethyl amino, dimethyl amino, diheptyl amino, cyclohexyl amino, benzylamino, etc.

Oxo groups (e.g., ##STR6## such as in ketones and aldehydes) Oxa groups(e.g., --O-- linkage in the main carbon chain)

Nitro groups

Imino groups (e.g., ##STR7## linkage in the main carbon chain) Cyanogroups

Fluoro groups

Chloro groups

Thioether groups (especially C₁₋₁₀ alkyl thioether)

Thia groups (e.g., --S-- linkage in the main carbon chain)

Carbohydrocarbyloxy groups (e.g., ##STR8## hydrocarbyl) Sulfonyl groups

Sulfinyl groups.

This list is intended to be merely illustrative and not exhaustive andthe omission of a certain class of substituent is not meant to requireits exclusion.

In general, if such substituents are present, there will not be morethan two for each 10 carbon atoms in the hydrocarbyl groups andpreferably not more than one for each 10 carbon atoms. Usually, thehydrocarbyl, hydrocarbyloxy, hydrocarbylmercapto, etc., groups will befree from any non-hydrocarbon groups due to economic considerations;that is, they will be characterized by the presence of only purelyhydrocarbyl groups which have only carbon and hydrogen atoms.

In the above formula, R¹ and R² can be saturated or ethylenicallyunsaturated and include alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl,arylalkyl, alkylaryl, etc. Suitable specific groups include methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, amyl, isoamyl, n-hexyl,2-ethylhexyl, 4-methyl-2-pentyl, allyl, 3-octenyl, cyclohexyl,chlorocyclohexyl, methylcyclohexyl, heptyl, n-octyl, isooctyl, tertiaryoctyl, nonyl, decyl, lauryl, cetyl, phenyl, bromophenyl,2,4-dichlorophenylethyl, chlorophenyl, nitrophenyl, methoxyphenyl,ethylphenyl, propylphenyl, butylphenyl, alkylated phenyl such aspropylene tetramer substituted phenyl, benzylphenylethyl, octenyl,cyclohexenyl, ethylcyclopenyl, N,N'-dibutylaminopropylphenyl,3-nitro-octyl, p-carboxyphenyl, phenoxyphenyl, naphthyl, alkylatednaphthyl such as propylene tetramer substituted naphthyl, acetylphenyl,2-ethoxyethyl, 6-ethylaminoheptyl, 4-cyanophenyl, 3,3,3-trifluoropropyl,dichloromethyl-3-thia-n-octyl, 2-methylmercapto naphthyl, 4-ethylsulfonyl-n-butyl, 4-phenylsulfinyl, phenyl, etc.

Methods for the preparation of such phosphorus acid compounds arewell-known to those of skill in the art and need not be repeated here.For convenience, however, reference is made to "OrganophosphorusCompounds" by G. M. Kosolapoff, John Wiley Publishers, 1950, N.Y., whichis incorporated herein by reference for its disclosure of methods forpreparing the phosphorus acid compounds. The following U.S. Patents arealso incorporated by reference for their disclosure of methods forpreparing the phosphorus acid compounds: 2,480,673; 2,552,570;2,618,597; 2,734,864; 2,734,865; 2,977,382; 3,000,822; 3,058,910;3,070,546; 3,073,781; 3,029,268; 3,081,261; 3,151,075; 3,361,668;3,185,728; 3,197,496; 3,210,275; 3,293,181 and 3,442,804.

A particularly preferred type of phosphorus acid compound useful in thisinvention is prepared by the reaction of phosphorus pentasulfide orhomologs thereof (e.g., P₄ S₁₀) with one or more hydroxy compounds whichcontain the organic groups R¹ and R₂ as defined above; that is, R¹ OHand R² OH or mixtures of two or more of any of these. An example of thistype of reaction is the reaction of phosphorus pentasulfide with ethylalcohol to produce, O,O-diethyl phosphorodithioic acid.

The aldehydes and ketones used in this invention are of the formula:##STR9## wherein R³ is hydrogen or hydrocarbyl of up to about 10 tencarbon atoms; R⁴ is hydrogen or lower alkyl; R⁵ and R⁶ are eachindependently selected from hydrogen, hydrocarbyl, hydrocarbyloxy andhydrocarbylmercapto of one to about 10 carbon atoms; R⁷ is hydrogen orhydrocarbyl of one to about 30 carbon atoms and n is zero or an integerof one to about 10.

Examples of the preferred aldehydes which can be used in this inventioninclude: acrolein, crotonaldehyde, 2-pentenal, 3-octenal, 5-decenal,2-ethyl-2-hexenal, 10-hexadecenal, methacrolein and cinnamaldehyde.Because of their commercial availability, acrolein and crotonaldehydeare especially applicable.

Examples of the preferred ketones which can be used in this inventioninclude: methylvinylketone, methylisopropenylketone,methylpropenylketone, mesityl oxide, 5-hexen-2-one,5-methyl-5-hexen-2-one, 5-hepten-2-one and 3-hepten-2-one.

It is often desirable to use a freshly distilled unsaturated aldehyde orketone containing none to about 2.0% by weight, preferably, none toabout 0.5% by weight of a polymerization inhibitor such as hydroquinone,di-tertiary-butyl catechol, 2,6-di-tertiary-butylphenol, etc.

In carrying out the reaction of the phosphorus acid and unsaturatedaldehyde or ketone to form the adduct, the reactants are broughttogether by contacting about 0.1 to about 1.0 equivalent of at least oneof the afore-described phosphorus acid compounds (One equivalent ofphosphorus acid is the molecular weight of potassium hydroxide,expressed in milligrams, divided by the acid number of the phosphorusacid compound. The acid number is the quantity of potassium hydroxide,expressed in milligrams, that is required to titrate the strong acidconstituents present in one gram of sample.) with about 1.2 to about 0.1equivalent of the afore-described unsaturated aldehydes or ketones (Oneequivalent of unsaturated aldehyde or ketone is the molecular weightdivided by the number of oxo groups present.). The reaction is normallycarried out for a period of about 0.1 to about 24 hours, generally,about 0.1 to about 5 hours, at a temperature in the range of about 10°C. up to the decomposition point of any component of the reactionmixture, preferably from about 10° C. to about 100° C.

Suitable substantially inert organic liquid solvent/diluents may be usedin the reaction and include such relatively low boiling saturatedhydrocarbons or aromatic liquids as hexane, heptane, benzene, toluene,xylene, etc., as well as high boiling materials such as solvent neutraloils, bright stocks and various types of synthetic and naturallubricating oil base stocks.

As used in the specification and the appended claims, the term"substantially inert" when used to refer to solvents, diluents, and thelike, is intended to mean that the solvent, diluent, etc., is inert tochemical or physical change under the conditions in which it is used soas not to materially interfere in an adverse manner with thepreparation, storage, blending and/or functioning of the compositions,additive, compound, etc. of this invention in the context of itsintended use. For example, small amounts of a solvent, diluent, etc. canundergo minimal reaction or degradation without preventing the makingand using of the invention as described herein. In other words, suchreaction or degradation, while technically discernible, would not besufficient to deter the practical worker of ordinary skill in the artfrom making and using the invention for its intended purposes."Substantially inert" as used herein is, thus, readily understood andappreciated by those of ordinary skill in the art.

While the reactants can be combined in any order to make theabove-mentioned phosphorus acid:unsaturated aldehyde or ketone adduct,it is preferable to add the unsaturated aldehyde or ketone to thephosphorus acid compound. Suitable agitation of the reaction mixture isdesirable, particularly when two liquid phases are present.

The reaction is often carried out in the absence of added catalystsand/or in the presence of an inert atmosphere. The progress of thereaction may be followed by determination of the acidity of the reactionmixture which drops to a low value as free acid is converted to neutralester.

It is often found, however, that the acidity of the reaction mixturecannot be reduced below an acid range of about 3 to about 15 even thoughmore unsaturated aldehyde or ketone is added. Therefore, it is oftenpreferred that if the determination of the acidity of the reactionmixture containing the adduct is in the acid range of about 3 to about15, that another reactant be employed. In this instance epoxides of upto about 22 carbon atoms such as ethylene oxide, propylene oxide,butylene oxide, styrene oxide and others can be used. Generally, thelower alkylene oxides such as ethylene oxide and propylene oxide areused. The epoxide reduces the acidity of the reaction mixture further byconverting free acid into neutral ester. The amount of epoxide usedranges from none to about 1.0 equivalent (One equivalent of epoxide isthe molecular weight divided by the number of epoxy groups, e.g.,##STR10## present), preferably from none to about 0.2 equivalent. Theepoxide addition is normally carried out for a period of about 0.01 toabout 1 hour, generally, about 0.01 to about 0.1 hour at a temperatureover the range of about 25° C. up to the decomposition point of anycomponent of the reaction mixture, preferably, from about 25° C. toabout 70° C.

The thiols or dithiols used in this invention with the above-mentionedphosphorus acid:unsaturated aldehyde or ketone adducts are of theformula:

    HS--R.sup.8 --H or HS--R.sup.8 --SH

wherein R⁸ is a hydrocarbyl group of one to about 30 carbon atoms.Preferably, R⁸ contains between one and 18 carbon atoms; morepreferably, R⁸ is a saturated hydrocarbon containing up to 12 carbonatoms.

Examples of the mercaptans which can be used in this invention include:methanethiol, ethanethiol, 2-propanethiol, 1-propanethiol,2-methyl-2propanethiol, 2-butanethiol, 2-methyl-1-propanethiol,1-butanethiol, 1-pentanethiol, 1-hexanethiol, 1-heptanethiol,1-octanethiol, n-dodecanethiol, t-dodecanethiol, cyclohexanethiol,1,2-ethanedithiol, benzenethiol, and t-benzenedithiol.

In carrying out the reaction of the phosphorus acid:unsaturated aldehydeor ketone adducts with the afore-described thiol or dithiol, thereactants are brought together by contacting about 0.1 to about 1.0equivalent of at least one of the previously described phosphorus acid:unsaturated aldehyde or ketone adducts (One equivalent of the phosphorusacid:unsaturated aldehyde or ketone adduct is the molecular weightdivided by the number of oxo groups present.) with about 1.2 to about0.1 equivalent of the previously described thiol or dithiol (Oneequivalent of thiol or dithiol is the molecular weight divided by thenumber of mercapto groups present.) in the presence of an acid catalyst;that is, a strong organic acid or a mineral acid such as para-toluenesulfonic acid, dithiophosphoric acid, Super Filtrol (a commerciallyavailable acidified clay), hydrochloric acid, etc. at a temperature inthe range of about 0° C. to about 100° C. The reaction is normallycarried out for a period of about 0.1 to about 24 hours, generally,about 0.1 to about 6 hours.

Suitable substantially inert organic liquid solvent/diluents can be usedin the reaction and include such relatively low boiling saturatedhydrocarbons or aromatic liquids as hexane, heptane, benzene, toluene,xylene, etc., as well as high boiling materials such as solvent neutraloils, bright stocks and various types of synthetic and naturallubricating oil base stocks. Factors governing the choice and use ofsuch materials are well-known to those of skill in the art. Normally,such a diluent will be used to facilitate heat control, handling,filtration, etc. It is often desirable to select a diluent which will becompatible with the other materials which are to be present in theenvironment where the product is intended to be used.

The inventive additives can be recovered from such solvent/diluents bysuch standard procedures as distillation, evaporation, precipitation,crystallization, dialysis, etc., when desired. Alternatively, if thesolvent/diluents are, for example, a base oil suitable for use in thefunctional fluid compositions of this invention, the product can be leftin the solvent/diluents and used to form the lubricating or functionalfluid composition as described below.

The above-mentioned phosphorus acid:unsaturated aldehyde or ketoneadduct, thiol or dithiol, acid catalyst and, optionally,solvent/diluents are combined and suitable agitation of the reactionmixture is desirable. The reaction mixture is held at about roomtemperature up to reflux temperature and the extent of the reaction ofthe thiol or dithiol with the adduct can be followed by analyticaldetermination of the percent unreacted mercaptan remaining in thereaction mixture. When the reaction is essentially complete, thereaction mixture can be stripped under a vacuum up to about 100° C. toremove the solvent/diluent (if such a relatively low boilingsolvent/diluent is used in the reaction) and then filtered throughdiatomaceous earth to give the desired saturated phosphorus-containingcomposition.

To prepare the unsaturated phosphorus-containing composition, thephosphorus acid:unsaturated aldehyde or ketone adduct, thiol or dithioland, optionally, solvent/diluents are combined and the reaction iscarried out in the presence of an acid catalyst; that is, a strongorganic acid or a mineral acid. Examples of suitable acid catalysts arepara-toluene sulfonic acid, dithiophosphoric acid, Super Filtrol (acommercially available acidified clay), hydrochloric acid, etc. Thereaction mixture is held at about room temperature up to refluxtemperature and the extent of the reaction of the thiol or dithiol withthe adduct can be followed by analytical determination of the percentunreacted mercaptan remaining in the reaction mixture. The water ofreaction is removed by azeotroping during the reaction. The reactionmixture can be stripped under a vacuum up to about 100° C. to remove thesolvent/diluent (if such a relatively low boiling solvent/diluent isused in the reaction) and then filtered through diatomaceous earth togive the desired composition.

Additionally, about 0.1 to about 4.0 moles of sulfur flowers can bemixed with about 1.0 to about 0.1 mole of the unsaturatedphosphorus-containing composition derived from the reaction, in thepresence of an acid catalyst as mentioned above, of a phosphorus acidcompound with an unsaturated aldehyde or ketone and with a thiol ordithiol and removal of the water of reaction. The reaction is normallycarried out for a period of about 0.1 to about 24 hours, generally,about 0.1 to about 4 hours, at a temperature in the range of about 110°C. up to the decomposition of the reaction mixture, preferably fromabout 160° C. to about 220° C. This additional sulfur treatment of thephosphorus-containing compositions, as described above, enhanceslubricant compositions by imparting additional antiwear andload-carrying properties to lubricant oils.

The following non-limiting examples are specific preferred embodimentsof the present invention. All references to percentages, parts, etc., inthe present specification and appended claims refer to percentages,parts, etc., by weight unless expressly stated otherwise.

EXAMPLE 1

A phosphorodithioic dialkylaryl acid is prepared by reacting at atemperature of about 149°-154° C. one mole P₂ S₅ with 4 moles of apropylene tetramer alkylated phenol. The resulting acid is characterizedby a phosphorus content of 4.70%, a sulfur content of 9.63% and an acidneutralization number to bromophenol blue (i.e., NNA (bpb)), asdetermined by ASTM Procedure D-974, of 80.

EXAMPLE 2

Freshly distilled acrolein (57 grams, 1.01 equivalents) is added to thephosphorodithioic dialkylaryl acid (643 grams, 0.92 equivalent) asprepared in Example 1 under a nitrogen purge over a 1-hour period atabout 60°-70° C. The material is then held at about 70° C. for 3 hours,cooled to room temperature and is characterized by a NNA(bpb) of 6. Thematerial is then stripped to about 80° C. under a vacuum of 20 torr. Thestripped material is then maintained at about 60° C. while propyleneoxide (7 grams, 0.12 mole) is added. The material is filtered throughdiatomaceous earth. The filtrate is characterized by a phosphoruscontent of 4.37%, a carbonyl content of 2.81% and a NNA(bpb) of 6.

EXAMPLE 3

Textile spirits (100 ml), an aliphatic petroleum naphtha having adistillation range of 63°-79° C. at 760 torr, n-dodecylmercaptan (12grams, 0.06 equivalent), the product of Example 2 (60 grams, 0.06equivalent), 0.1 gram paratoluene sulfonic acid and 11 grams Linde 3Amolecular sieve pellets are held at about 25°-30° C. for 20 hours. Thematerial is filtered through paper to remove the sieves, stripped toabout 80° C. under a vacuum of 30 torr and then filtered throughdiatomaceous earth. The product is characterized by a sulfur content of10.25%, a phosphorus content of 3.49% and a NNA(bpb) of 3.

EXAMPLE 4

A phosphorodithioic dialkyl acid is prepared by reacting at atemperature of about 110°-118° C. one mole P₂ S₅ with 4 moles of decylalcohol:isooctyl alcohol in a (30:70) weight ratio. The resulting acidis characterized by a phosphorus content of 7.9%, a sulfur content of16.2% and a NNA(bpb) of 131.

EXAMPLE 5

Freshly distilled acrolein (130 grams, 2.33 equivalents) is added to thephosphorodithioic dialkyl acid (905 grams, 2.12 equivalents) as preparedin Example 4 under a nitrogen purge over a 1-hour period at about60°-70° C. The material is held at about 60°-70° C. for 3.5 hours,cooled to room temperature and is characterized by a NNA(bpb) of 5. Thematerial is then stripped to about 48° C. under a vacuum of 24 torr. Atabout 40° C. propylene oxide (10 grams, 0.17 equivalent) is added andthe material is filtered through diatomaceous earth. The filtrate ischaracterized by a phosphorus content of 5.80%, a carbonyl content of5.43% and a NNA(bpb) of 1.2.

EXAMPLE 6

Benzene (200 ml), the product of Example 5 (229 grams, 0.48 mole),n-dodecylmercaptan (97 grams, 0.48 mole) and 0.5 gram para-toluenesulfonic acid is held at reflux, removing by azeotroping, 58% of thetheory water. The material is stripped to about 90° C. under a vacuum of28 torr and then filtered through diatomaceous earth. The filtrate ischaracterized by a sulfur content of 14.7%, a phosphorus content of4.98%, a carbonyl content of 1.33%, a mercaptan content of 2.25% and aNNA(bpb) of 4.5.

EXAMPLE 7

Sulfur flowers (2.6 grams, 0.08 mole) and the product of Example 3 (47grams, 0.04 mole) is held at about 185°-190° C. for 2 hours. Thematerial is cooled to about 80° C., purged with nitrogen and thenfiltered through diatomaceous earth. The product is characterized by asulfur content of 12.1%.

EXAMPLE 8

The procedure of Example 2 is followed except freshly distilledcrotonaldehyde (71 grams, 1.01 equivalents) is substituted for theacrolein.

EXAMPLE 9

The procedure of Example 6 is followed except freshly distilledcrotonaldehyde (164 grams, 2.33 equivalents) is substituted for theacrolein.

EXAMPLES 10 AND 11

In the same manner as in Example 5, freshly distilled crotonaldehyde andmethylvinyl ketone is substituted for the acrolein on the same molarbasis, respectively, to form the desired intermediates.

EXAMPLES 12 and 13

The intermediates of Examples 10 and 11 are further reacted by followingthe procedure as described in Example 6 to form the desired products.

EXAMPLE 14

The procedure of Example 6 is followed except 1,2-ethanedithiol (24grams, 0.24 equivalent) is substituted for the n-dodecylmercaptan.

Although the phosphorus-containing compositions of this invention asdescribed above are, in themselves, useful as extreme pressure,anti-wear and load-carrying agents, they are nevertheless susceptible toimprovement by the addition of one or more chemical additives tosupplement their action to give the properties desired when incorporatedinto the lubricating and hydraulic compositions of this invention. Suchsupplemental agents may be illustrated by the lead, nickel or Group IIAand IIB metal phosphorodithioate salts in which the metal may bemagnesium, calcium, barium, strontium, zinc, cadmium, lead or nickel.Zinc phosphorodithioates are particularly preferred. Other types ofextreme pressure agents which can find use in the lubricating oilcompositions of this invention include chlorinated waxes, sulfurized orphosphosulfurized fatty acid esters, di- or trihydrocarbyl phosphitesand phosphates, dihydrocarbon polysulfides and metal dithiocarbamates.These and other useful extreme pressure agents are described in moredetail in the books both entitled "Lubricant Additives" by Smith andSmalheer (published by the Lezius-Hiles Co., of Cleveland, Ohio) and byM. W. Raney (published by the Noyes Data Corporation of Park Ridge, NewJersey) pages 146-212, both of which are incorporated herein byreference for their disclosure of additional extreme pressure agentswhich can be used in conjunction with the additives of the presentinvention.

Still another type of additive which can be useful in the lubricatingoil compositions of the present invention is one or more rust-inhibitingagents. A very effective rust-inhibiting agent is the alkyl oralkenyl-substituted acids having the structure. ##STR11## in which R ishydrocarbon radical having at least 10 carbon atoms. Preferably, R is adodecenyl group. When a rust-inhibiting agent is used in the lubricantcompositions of this invention only a small amount is needed. It can beas little as about 0.01 part and seldom exceeds about 2 parts per 100parts of the lubricant composition.

Demulsifiers may also be included in the lubricant compositions of thisinvention. The preferred demulsifiers are the commercial alkylatedphenoxypoly(alkyleneoxy)alkanol compounds such asnonylphenoxypoly(ethyleneoxy)ethanol. Generally, the amount ofdemulsifier used can be as little as about 0.01 part and seldom exceedsabout 2 parts per 100 parts of the lubricant composition.

The lubricant compositions of this invention can also contain aconventional foam inhibitor such as a commercial dialkyl siloxanepolymer.

Oxidation inhibitors can also be included in the lubricating oilcompositions of this invention. Hindered phenols such as2,4-di-t-butyl-6-methylphenol, 4,4'-methylene-(2,6-di-t-pentylphenol),and 2,6-di-t-octyl-4-secondary butylphenol are representative of usefuloxidation inhibitors. The concentration of such oxidation inhibitors inthe lubricating oil compositions of this invention is usually betweenabout 0.01 to about 2 parts per 100 parts of the lubricant composition.

The phosphorus-containing compounds of this invention can be effectivelyemployed in a variety of lubricating compositions based on diverse oilsof lubricating viscosity such as natural or synthetic lubricating oils,or suitable mixtures thereof. The lubricating compositions contemplatedinclude principally crankcase lubricating oils for spark-ignited andcompression-ignited internal combustion engines including automobile andtruck engines, two-cycle engine lubricants, aviation piston engines,marine and railroad diesel engines, and the like. However, automatictransmission fluids, transaxle lubricants, gear lubricants,metal-working lubricants, hydraulic fluids, and other lubricating oiland grease compositions can benefit from the incorporation of thepresent phosphorus-containing compounds.

Natural oils include animal oils and vegetable oils (e.g., castor oil,lard oil) as well as solvent-refined or acid-refined mineral lubricatingoils of the paraffinic, naphthenic or mixed paraffinic-naphthenic types.Oils of lubricating viscosity derived from coal or shale are also usefulbase oils. Synthetic lubricating oils include hydrocarbon oils andhalo-substituted hydrocarbon oils such as polymerized andinterpolymerized olefins (e.g., polybutylenes, polypropylene,propylene/isobutylene copolymers, chlorinated polybutylenes, etc.);alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes,dinonylbenzenes, di-(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g.,biphenyls, terphenyls, etc.); and the like. Alkylene oxide polymers andinterpolymers and derivatives thereof, where the terminal hydroxy groupshave been modified by esterification, etherification, etc., constituteanother class of known synthetic lubricating oils. These are exemplifiedby the oils prepared through polymerization of ethylene oxide orpropylene oxide, the alkyl and aryl ethers of these polyoxyalkylenepolymers (e.g., methyl polyisopropylene glycol ether having an averagemolecular weight of 1000, diphenyl ether of polyethylene glycol having amolecular weight of 500-1000, diethyl ether of polypropylene glycolhaving a molecular weight of 1000-1500, etc.) or mono- andpolycarboxylic esters thereof, for example, the acetic acid esters,mixed C₃ -C₈ fatty acid esters, or the C₁₃ Oxo acid diester oftetraethylene glycol. Another suitable class of synthetic lubricatingoils comprises the esters of dicarboxylic acid (e.g., phthalic acid,succinic acid, maleic acid, azeleic acid, suberic acid, sebacic acid,fumaric acid, linoleic acid dimer, etc.) with a variety of alcohols,(e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2 -ethylhexylalcohol, pentaerythritol, etc.). Specific examples of these estersinclude dibutyl adipate, di(2ethylhexyl) sebacate, di-n-hexyl fumarate,dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctylphthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyldiester of linoleic acid dimer, the complex ester formed by reacting onemole of sebacic acid with two moles of tetraethylene glycol and twomoles of 2-ethylhexanoic acid, and the like. Silicone-based oils such asthe polyalkyl-, polyaryl-, polyalkyloxy-, or polyaryloxy-siloxane oilsand silicate oils comprise another useful class of synthetic lubricants(e.g., tetraethyl silicate, tetraisopropyl silicate, tetra(2-ethylhexyl) silicate, tetra(4-methyl-2-tetraethyl)silicate,tetra(p-tert-butylphenyl)silicate, hexyl(4-methyl-2-pentoxy)disiloxane,poly(methyl)siloxane, poly(methyl-phenyl)siloxane, etc. Other syntheticlubricating oils include liquid esters of phosphorus-containing acid(e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester ofdecanephosphonic acid, etc.), polymeric tetrahydrofurans, and the like.

The lubricating oil compositions of this invention comprise a majoramount of oil and a minor, load-carrying improving amount of at leastone additive composition of the invention. Generally, this amount willbe about 0.5 to about 20 parts additive per 100 parts oil.

Exemplary of these lubricating oil compositions are the following:

EXAMPLE 15

A lubricating composition consisting of 98 parts 200 Neutral oil, twoparts of the additive composition of Example 6 and 40 parts per million(i.e., ppm) of a commercial silicone-based anti-foam agent.

EXAMPLE 16

A hydraulic fluid composition consisting of 98.95 parts 350 Neutral oil,1.00 part of the additive composition of Example 6, 0.025 part of an oilsolution containing 40% polypropylene tetramer alkenylated succinic acidas a rust inhibitor and 0.025 part of nonylphenoxy poly(ethyleneoxy)ethanol as a demulsifier.

What is claimed is:
 1. A lubricating composition comprising a majorproportion of a lubricating oil and a minor effective proportion of atleast one additive corresponding to the formula:

    Y.sup.a --S--Y.sup.b

wherein Y^(a) corresponds to ##STR12## and Z is ##STR13## or ##STR14##wherein each R¹ and R² is independently a member selected from the groupconsisting of hydrocarbyl, hydrocarbyloxy and hydrocarbylmercapto of oneto about 30 carbon atoms; R³ is hydrogen or hydrocarbyl of up to about10 carbon atoms; R⁴ is hydrogen or lower alkyl; R⁵ and R⁶ are eachindependently selected from hydrogen, hydrocarbyl, hydrocarbyloxy andhydrocarbylmercapto of one to about 10 carbon atoms; R⁷ is hydrogen orhydrocarbyl of one to about 30 carbon atoms; each X is independentlyoxygen or divalent sulfur; n is zero or an integer of one to about 10;n' is zero or an integer of one to about 9; Y^(b) is

    --R.sup.8 --H

or

    --R.sup.8 --S--R.sup.9

wherein R⁸ is a divalent hydrocarbyl group of one to about 30 carbonatoms and R⁹ is hydrogen or Y^(a).
 2. The composition of claim 1 whereinR¹ and R² are each independently hydrocarbyloxy groups containing one toabout 30 carbon atoms and each X is oxygen.
 3. The composition of claim1 wherein R¹ and R² are each independently hydrocarbyloxy groupscontaining one to about 30 carbon atoms and each X is a divalent sulfuratom.
 4. The composition of claim 3 wherein R¹ and R² are eachindependently alkyloxy or alkylphenoxy groups containing one to about 18carbon atoms.
 5. The composition of claim 4 wherein Z is ##STR15## andR³, R⁴ and R⁷ are each independently hydrogen or methyl and n is zero.6. The composition of claim 5 wherein Y^(b) is --R⁸ --S--R⁹ and R⁸ is adivalent hydrocarbyl group containing one to about 18 carbon atoms andR⁹ is hydrogen or Y^(a).
 7. The composition of claim 6 wherein R⁹ isY^(a).
 8. The composition of claim 5 wherein Y^(b) is --R⁸ --H and R⁸ isa divalent hydrocarbyl group containing one to about 18 carbon atoms. 9.A lubricating composition comprising a major proportion of a lubricatingoil and a minor effective proportion of at least one additivecorresponding to the formula: ##STR16## wherein R¹ and R² are eachindependently alkyloxy or alkylphenoxy groups containing about 18 carbonatoms, R⁷ is hydrogen or methyl and R⁸ is an alkylene group containingabout 12 carbon atoms.
 10. The composition of claim 4 wherein Z is##STR17## and R³ and R⁷ are each independently hydrogen or methyl. 11.The composition of claim 1 wherein Y^(b) is --R⁸ --S--R⁹ and R⁸ is adivalent hydrocarbyl group containing one to about 18 carbon atoms andR⁹ is hydrogen or Y^(a).
 12. The composition of claim 11 wherein R⁹ isY^(a).
 13. The composition of claim 10 wherein Y^(b) is --R⁸ --H and R⁸is a divalent hydrocarbyl group containing one to about 18 carbon atoms.14. A lubricating composition comprising a major proportion of alubricating oil and a minor effective proportion of at least oneadditive corresponding to the formula: ##STR18## wherein R¹ and R² areeach independently alkyloxy or alkylphenoxy groups containing about 18carbon atoms, R⁷ is hydrogen or methyl and R⁸ is an alkylene groupcontaining about 12 carbon atoms.
 15. A concentrate which comprises asubstantially inert, normally liquid organic diluent and from about 10%to about 90% of at least one additive corresponding to the formula:

    Y.sup.a --S--Y.sup.b

wherein Y^(a) corresponds to ##STR19## and Z is ##STR20## wherein eachR¹ and R² is independently a member selected from the group consistingof hydrocarbyl, hydrocarbyloxy and hydrocarbylmercapto of one to about30 carbon atoms; R³ is hydrogen or hydrocarbyl of up to about 10 carbonatoms; R⁴ is hydrogen or lower alkyl; R⁵ and R⁶ are each independentlyselected from hydrogen, hydrocarbyl, hydrocarbyloxy andhydrocarbylmercapto of one to about 10 carbon atoms; R⁷ is hydrogen orhydrocarbyl of one to about 30 carbon atoms; each X is independentlyoxygen or divalent sulfur; n is zero or an integer of one to about 10;n' is zero or an integer of one to about 9; Y^(b) is

    --R.sup.8 --H or --R.sup.8 --S--R.sup.9

wherein R⁸ is a divalent hydrocarbyl group of one to about 30 carbonatoms and R⁹ is hydrogen or Y^(a).
 16. A concentrate according to claim15 wherein R¹ and R² are each independently alkyloxy or alkylphenoxygroups containing one to about 18 carbon atoms; each X is a divalentsulfur atom; Z is ##STR21## and R³, R⁴ and R⁷ are each independentlyhydrogen or methyl; n is zero; Y^(b) is --R⁸ --S--R⁹ wherein R⁸ is adivalent hydrocarbyl group containing one to about 18 carbon atoms andR⁹ is hydrogen or Y^(a).
 17. A concentrate according to claim 15 whereinY^(b) is --R⁸ --H and R⁸ is a divalent hydrocarbyl group containing oneto about 18 carbon atoms.
 18. A concentrate according to claim 15wherein R¹ and R² are each independently alkyloxy or alkylphenoxy groupscontaining one to about 18 carbon atoms; each X is a divalent sulfuratom; Z is ##STR22## and R³ and R⁷ are each independently hydrogen ormethyl; Y^(b) is --R⁸ --S--R⁹, wherein R⁸ is a divalent hydrocarbylgroup containing one to about 18 carbon atoms and R⁹ is hydrogen orY^(a).
 19. A concentrate according to claim 15 wherein Y^(b) is --R⁸ --Hand R⁸ is a divalent hydrocarbyl group containing one to about 18 carbonatoms.